Electrically operated power steering controller and adjusting method of driving electric current offset in this controller

ABSTRACT

The invention proposes an electrically operated power steering controller for inputting a driving electric current offset value of higher accuracy and being able to make an offset correction of a driving electric current by using this driving electric current offset value of higher accuracy, and an adjusting method of this driving electric current offset. Therefore, an electric motor driving electric current measuring device of accuracy higher than that of an electric motor driving electric current detector assembled into a controller CNT is prepared separately from this electric motor driving electric current detector. The driving electric current offset value of high accuracy is outputted by this electric motor driving electric current measuring device. An input device for receiving the driving electric current offset value of high accuracy from the driving electric current measuring device is arranged in an offset correcting device or an offset signal generator within the controller.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an electrically operated power steeringcontroller for controlling the operation of an electric motor forgenerating auxiliary steering torque and an adjusting method of itsdriving electric current offset.

2. Background Art

The electrically operated power steering controller disclosed in FIG. 2of JP08-175405A includes an offset correcting means as well as a targetsignal generating means, an electric current detecting means and a drivecontrol means. This electrically operated power steering controllercontrols the operation of the electric motor for generating theauxiliary steering torque. The target signal generating means calculatesa driving electric current target value with respect to the electricmotor, and generates a driving electric current target signalrepresenting this driving electric current target value. The electriccurrent detecting means detects the driving electric current value ofthe electric motor, and generates a driving electric current detectingsignal representing this driving electric current value.

In this electrically operated power steering controller, the drivingelectric current of the electric motor is basically controlled by thedriving control means such that the deviation between the drivingelectric current target value calculated by the target signal generatingmeans and the driving electric current value detected by the electriccurrent detecting means is zero. However, in the electrically operatedpower steering controller, the driving electric current value detectedfrom the electric motor includes a driving electric current offset valueeven when the driving electric current target value with respect to theelectric motor is zero. Therefore, the offset correcting means disclosedin the above prior art stores the driving electric current offset valuewhen this driving electric current target value is zero, and makes anoffset correction in consideration of this driving electric currentoffset value.

However, the offset correcting means disclosed in the above prior artstores the driving electric current offset value by using an output fromthe electric current detecting means for detecting the driving electriccurrent value from the electric motor as it is. However, this electriccurrent detecting means is a mass-produced product assembled into theelectrically operated power steering controller, and its electriccurrent detecting accuracy cannot be set to be so high from therestriction of cost. Therefore, the accuracy of the stored drivingelectric current offset value becomes low so that the accuracy of theoffset correction also becomes low.

SUMMARY OF THE INVENTION

This invention proposes an improved electrically operated power steeringcontroller able to introduce a more precise driving electric currentoffset value.

Further, this invention proposes an adjusting method of the drivingelectric current offset in the electrically operated power steeringcontroller able to introduce a more precise driving electric currentoffset value into the electrically operated power steering controller.

According to a first aspect of this invention, it is proposed anelectrically operated power steering controller for controlling theoperation of an electric motor for generating auxiliary steering torque.The electrically operated power steering controller according to thefirst aspect includes driving electric current target signal generatingmeans, driving electric current detecting means, offset correcting meansand electric motor driving control means. The driving electric currenttarget signal generating means generates a driving electric currenttarget signal representing a driving electric current target value Itagfor the electric motor. The driving electric current detecting meansgenerates a driving electric current detecting signal representing adriving electric current value Imtr of the electric motor. The offsetcorrecting means generates a corrected driving electric current signalrepresenting a corrected driving electric current value Iamd provided bycorrecting the driving electric current value Imtr by using a drivingelectric current offset value Ioff of the electric motor when thedriving electric current target value Itag is set to zero. The electricmotor driving control means controls the operation of the electric motoron the basis of the driving electric current target signal and thecorrected driving electric current signal. In the electrically operatedpower steering controller according to the first aspect, the offsetcorrecting means has first and second input sections, the drivingelectric current detecting signal is inputted to the first inputsection, and input means for inputting a driving electric current offsetsignal representing the driving electric current offset value Ioff isconnected to the second input section.

According to a second aspect of this invention, it is proposed anelectrically operated power steering controller for controlling theoperation of an electric motor for generating auxiliary steering torque.The electrically operated power steering controller according to thesecond aspect includes driving electric current target signal generatingmeans, driving electric current detecting means, offset signalgenerating means, arithmetic means and electric motor driving controlmeans. The driving electric current target signal generating meansgenerates a driving electric current target signal representing adriving electric current target value Itag for the electric motor. Thedriving electric current detecting means generates a driving electriccurrent detecting signal representing a driving electric current valueImtr of the electric motor. The offset signal generating means generatesa driving electric current offset signal representing a driving electriccurrent offset value Ioff of the electric motor when the drivingelectric current target value Itag is set to zero. The arithmetic meanscalculates an arithmetic value Iest=Itag−(Imtr−Ioff) on the basis of thedriving electric current target signal, the driving electric currentdetecting signal and the driving electric current offset signal. Theelectric motor driving control means controls the operation of theelectric motor on the basis of the arithmetic value. The electricallyoperated power steering controller according to the second aspect isconstructed such that the driving electric current detecting signal andthe driving electric current offset signal are supplied to thearithmetic means from routes different from each other, and input meansfor inputting the offset electric current signal representing thedriving electric current offset value Ioff is connected to the offsetsignal generating means.

According to the first aspect, it is also proposed an adjusting methodof a driving electric current offset in an electrically operated powersteering controller including driving electric current target signalgenerating means, driving electric current detecting means, offsetcorrecting means and electric motor driving control means. The drivingelectric current target signal generating means generates a drivingelectric current target signal representing a driving electric currenttarget value Itag for an electric motor for generating auxiliarysteering torque. The driving electric current detecting means generatesa driving electric current detecting signal representing a drivingelectric current value Imtr of the electric motor. The offset correctingmeans generates a corrected driving electric current signal representinga corrected driving electric current value Iamd provided by correctingthe driving electric current value Imtr by using a driving electriccurrent offset value Ioff of the electric motor when the drivingelectric current target value Itag is set to zero. The electric motordriving control means controls the operation of the electric motor onthe basis of the driving electric current target signal and thecorrected driving electric current signal. In the electrically operatedpower steering controller according the first aspect, the offsetcorrecting means has first and second input sections, the drivingelectric current detecting signal is inputted to the first inputsection, and input means for inputting an offset electric current signalrepresenting the driving electric current offset value Ioff is connectedto the second input section. The adjusting method according to the firstaspect uses driving electric current measuring means different from thedriving electric current detecting means. In the adjusting methodaccording to the first aspect, the offset electric current signalrepresenting the driving electric current offset value Ioff is inputtedto the offset correcting means through the input means by this drivingelectric current measuring means.

According to the second aspect, it is also proposed an adjusting methodof a driving electric current offset in an electrically operated powersteering controller including driving electric current target signalgenerating means, driving electric current detecting means, offsetsignal generating means, arithmetic means and electric motor drivingcontrol means. The driving electric current target signal generatingmeans generates a driving electric current target signal representing adriving electric current target value Itag for an electric motor forgenerating auxiliary steering torque. The driving electric currentdetecting means generates a driving electric current detecting signalrepresenting a driving electric current value Imtr of the electricmotor. The offset signal generating means generates a driving electriccurrent offset signal representing a driving electric current offsetvalue Ioff of the electric motor when the driving electric currenttarget value Itag is set to zero. The arithmetic means calculates anarithmetic value Iest=Itag−(Imtr−Ioff) on the basis of the drivingelectric current target signal, the driving electric current detectingsignal and the driving electric current offset signal. The electricmotor driving control means controls the operation of the electric motoron the basis of the arithmetic value. The electrically operated powersteering controller according to the second aspect is constructed suchthat the driving electric current detecting signal and the drivingelectric current offset signal are supplied to the arithmetic means fromroutes different from each other, and input means is connected to theoffset signal generating means. The adjusting method according to thesecond aspect uses driving electric current measuring means differentfrom the driving electric current detecting means, and the offsetelectric current signal representing the driving electric current offsetvalue Ioff is inputted to the offset signal generating means through theinput means by this driving electric current measuring means.

In the electrically operated power steering controller corresponding tothe first aspect of this invention, the offset correcting means has thefirst and second input sections, and the driving electric currentdetecting signal is inputted to the first input section, and the inputmeans for inputting the driving electric current offset signalrepresenting the driving electric current offset value Ioff is connectedto the second input section. Accordingly, the driving electric currentoffset signal representing the driving electric current offset value ofhigh accuracy can be introduced from this input means irrespective ofthe driving electric current detecting means. Thus, the operation of theelectric motor can be controlled with higher accuracy by using thisdriving electric current offset value of high accuracy.

Further, in the electrically operated power steering controllercorresponding to the second aspect of this invention, the electricallyoperated power steering controller is constructed such that the drivingelectric current detecting signal and the driving electric currentoffset signal are supplied to the arithmetic means from routes differentfrom each other, and the input means for inputting the driving electriccurrent offset signal representing the driving electric current offsetvalue Ioff is connected to the offset signal generating means.Accordingly, the driving electric current offset signal representing thedriving electric current offset value of high accuracy can be introducedfrom this input means irrespective of the driving electric currentdetecting means. Thus, the operation of the electric motor can becontrolled with higher accuracy by using this driving electric currentoffset value of high accuracy.

In the adjusting method of the driving electric current offset in theelectrically operated power steering controller corresponding to thefirst aspect of this invention, the driving electric current measuringmeans different from the driving electric current detecting means isused, and the driving electric current offset signal representing thedriving electric current offset value Ioff is inputted to the offsetcorrection means through the input means by this driving electriccurrent measuring means. Accordingly, the driving electric currentoffset signal representing the driving electric current offset value ofhigh accuracy can be introduced into the electrically operated powersteering controller by setting the measuring accuracy of the drivingelectric current measuring means to be higher than the detectingaccuracy of the driving electric current detecting means. Thus, theelectrically operated power steering controller can control theoperation of the electric motor with higher accuracy by using thisdriving electric current offset value of higher accuracy.

Further, in the adjusting method of the driving electric current offsetin the electrically operated power steering controller corresponding tothe second aspect of this invention, the driving electric currentmeasuring means different from the driving electric current detectingmeans is used, and the driving electric current offset signalrepresenting the driving electric current offset value Ioff is inputtedto the offset signal generating means through the input means by thisdriving electric current measuring means. Accordingly, the drivingelectric current offset signal representing the driving electric currentoffset value of high accuracy can be introduced into the electricallyoperated power steering controller by setting the measuring accuracy ofthe driving electric current measuring means to be higher than thedetecting accuracy of the driving electric current detecting means.Thus, the electrically operated power steering controller can controlthe operation of the electric motor with higher accuracy by using thisdriving electric current offset value of higher accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an embodiment 1 of an electricallyoperated power steering controller in this invention;

FIG. 2 is a flow chart showing an adjusting method of a driving electriccurrent offset of the electrically operated power steering controller ofthe embodiment 1;

FIG. 3 is a block diagram showing an embodiment 2 of the electricallyoperated power steering controller in this invention; and

FIG. 4 is a flow chart showing an adjusting method of the drivingelectric current offset of the electrically operated power steeringcontroller of the embodiment 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some embodiments of this invention will next be explained with referenceto the drawings.

Embodiment 1

This embodiment 1 is an embodiment corresponding to a first aspect ofthis invention, and includes an electrically operated power steeringcontroller in this invention, and an adjusting method of a drivingelectric current offset in the electrically operated power steeringcontroller in this invention.

FIG. 1 is a block diagram showing the electrically operated powersteering controller in this embodiment 1. This electrically operatedpower steering controller is mounted to an automobile, and includes acontroller CNT, a direct current power source BAT, an electric motor MTRand an electric motor driving electric current measuring means MCM. Thecontroller CNT, the direct current power source BAT and the electricmotor MTR are mounted to the automobile, but the electric motor drivingelectric current measuring circuit MCM is arranged in a manufacturingfactory or a repairing factory of the automobile or automobile parts.When an adjusting process of the driving electric current offset isexecuted with respect to the electrically operated power steeringcontroller, the electric motor driving electric current measuringcircuit MCM is combined with the controller CNT, the direct currentpower source BAT and the electric motor MTR. For example, the directcurrent power source BAT is a battery mounted to the automobile.

The electric motor MTR is assembled into a steering mechanism of theautomobile, and gives auxiliary steering torque for assisting steeringtorque provided by a driver to the steering mechanism. The steeringmechanism of the automobile has a steering handle operated by thedriver, a steering shaft operated by this steering handle, and a gearbox connected to this steering shaft. The steering mechanism steers asteering wheel of the automobile through the steering shaft and the gearbox on the basis of the steering torque given to the steering handle.The electric motor MTR is connected to the steering shaft through aspeed reduction gear, and gives the auxiliary steering torque forassisting the steering torque to the steering shaft. For example, adirect current electric motor is used as this electric motor MTR.

The controller CNT includes a power driving circuit 100 with respect tothe electric motor MTR, and a control unit 200 for controlling theoperation of this power driving circuit 100. The power driving circuit100 includes a switch circuit 110 connected to the direct current powersource BAT and switching the polarities of its direct current voltage, agate driving circuit 120 with respect to this switch circuit 110, and anelectric motor driving electric current detecting circuit 130.

The switch circuit 110 includes two power switch elements 11A, 11Bconnected in series, and power switch elements 11C, 11D connected inseries. The connecting portion between the power switch elements 11A and11B constitutes a first output terminal 11 a. The connecting portionbetween the power switch elements 11C and 11D constitutes a secondoutput terminal 11 b.

The electric motor MTR is connected between the first output terminal 11a and the second output terminal 11 b, and the operation of the electricmotor MTR is controlled by the switch circuit 110 in a first or secondcontrol state. In the first control state, for example, the electricmotor MTR is rotated in the positive direction in a controlled drivingduty ratio. In the second control state, for example, the electric motorMTR is rotated in the reverse direction in the controlled driving dutyratio.

In the first control state, both the power switch elements 11B, 11C areturned off, and both the power switch elements 11A, 11D are periodicallyturned on in the controlled driving duty ratio. When the power switchelements 11A, 11D are turned on in this first control state, an electriccurrent is flowed from the power switch element 11A to the power switchelement 11D via the first output terminal 11 a, the electric motor MTRand the second output terminal 11 b. When the electric current flowed tothe electric motor MTR is set to have a positive polarity in this firstcontrol state, the electric motor MTR is rotated in the positivedirection in the driving duty ratio and is operated by the electriccurrent of the positive polarity in the first control state.

In the second control state, both the power switch elements 11A, 11D areturned off, and both the power switch elements 11B, 11C are periodicallyturned on in the controlled duty ratio. When the power switch elements11B, 11C are turned on in this second control state, the electriccurrent is flowed from the power switch element 11C to the power switchelement 11B via the second output terminal 11 b, the electric motor MTRand the first output terminal 11 a. When the electric current flowed tothe electric motor MTR in this second control state is set to have areverse polarity, the electric motor MTR is rotated in the reversedirection in the driving duty ratio and is operated by the electriccurrent of the reverse polarity in the second control state.

For example, a power MOSFET is used in the power switch elements 11A,11B, 11C, 11D. This power MOSFET has a gate for controlling its turningon and off operations, and attains a turning-on state when a drivingpulse is given to the gate. A gate driving circuit 120 has driving pulsecircuits 12A, 12B, 12C, 12D for supplying the driving pulse to therespective gates of the power switch elements 11A, 11B, 11C, 11D.

The electric motor driving electric current detecting circuit 130generates a driving electric current detecting signal SImtr representinga driving electric current value Imtr of the electric motor MTR. Thiselectric motor driving electric current detecting circuit 130 includes adetecting resistor RD and a driving electric current detecting means 13.The detecting resistor RD is connected between the first output terminal11 a and the electric motor MTR. The driving electric current detectingmeans 13 detects the voltage generated at both the ends of a detectingresistor 21 on the basis of the driving electric current value Imtr ofthe electric motor MTR, and generates the driving electric currentdetecting signal SImtr representing the driving electric current valueImtr.

The electric motor driving electric current detecting circuit 130 isassembled into the controller CNT. The controller CNT is a mass-producedcontroller mounted to the automobile and including the electric motordriving electric current detecting circuit 130. There is a restrictionin cost of this controller CNT to mass-produce this controller CNT.Since this restriction of cost is similarly applied to the electricmotor driving electric current detecting circuit 130, the electric motordriving electric current detecting circuit 130 and an A/D converter 51are also made at relatively low cost, and its detecting accuracy of thedriving electric current value Imtr is not so high.

Similar to the electric motor driving electric current detecting circuit130, the electric motor driving electric current measuring circuit MCMmeasures the driving electric current value Imtr of the electric motorMTR. However, this electric motor driving electric current measuringcircuit MCM is not mounted to the automobile, but is arranged in amanufacturing factory of the automobile or automobile parts or arepairing factory of the automobile. Only a small number of electricmotor driving electric current measuring circuits MCM are arranged inthe manufacturing factory of the automobile or the automobile parts, orthe repairing factory, and are not restricted so much in cost.Accordingly, the electric motor driving electric current measuringcircuit MCM is constructed so as to generate a driving electric currentmeasuring signal SIPmtr in which the driving electric current value Imtris measured with high accuracy in comparison with the electric motordriving electric current detecting circuit 130. This electric motordriving electric current measuring circuit MCM has an electric motordriving electric current measuring means 300 and an A/D converter 301.This electric motor driving electric current measuring means 300 isconnected between the second output terminal 11 b and the electric motorMTR, and outputs a driving electric current measuring signal (analog) ofhigh accuracy. The A/D converter 301 of high accuracy is connected tothe output of the electric motor driving electric current measuringmeans 300, and this A/D converter 301 outputs the driving electriccurrent measuring signal SIPmtr of high accuracy in which the drivingelectric current measuring signal of high accuracy is converted into adigital format.

The control unit 200 is constructed with a microcomputer 20 as a center.This microcomputer 20 includes a driving electric current target signalgenerating means 30, an electric motor driving control means 40, anoffset correcting means 50, an arithmetic means 60 and a ROM 70. The ROM70 is a read only memory for storing a program required in themicrocomputer 20. The operations of the driving electric current targetsignal generating means 30, the electric motor driving control means 40,the offset correcting means 50 and the arithmetic means 60 arerespectively executed by using a CPU and a RAM of the microcomputer 20on the basis of the program stored to the ROM 70.

The driving electric current target signal generating means 30calculates a driving electric current target value Itag with respect tothe electric motor MTR, and generates a driving electric current targetsignal SItag representing this driving electric current target valueItag. This driving electric current target signal generating means 30has two input sections 30 a, 30 b and one output section 30 c. Asteering torque signal ST representing steering torque T from a steeringtorque sensor 31 is fetched into the input section 30 a through an A/Dconverter 32. Various kinds of signals are fetched from a network 33within the automobile into the input section 30 b through a control areanetwork (CAN) 34. A vehicle speed signal SV representing a vehicle speedV of the automobile, a steering angle signal Sθ representing thesteering angle θ of a steering handle, and a steering speed signal Sωsrepresenting a rotating speed ωs of the steering shaft of the steeringmechanism are transmitted in the network 33. The driving electriccurrent target signal generating means 30 calculates the drivingelectric current target value Itag on the basis of the steering torquesignal ST, the vehicle speed signal SV, the steering angle signal Sθ andthe steering speed signal Sωs, and generates the driving electriccurrent target signal SItag representing this driving electric currenttarget value Itag in the output section 30 c. This driving electriccurrent target signal SItag is supplied to the arithmetic means 60. Thisarithmetic means 60 outputs a driving electric current arithmetic valueIest.

The electric motor driving control means 40 has one input section 40 aand two output sections 40 b, 40 c. The input section 40 a is connectedto the arithmetic means 60. The output sections 40 b, 40 c arerespectively connected to pulse width modulating circuits (PWM) 41, 42.These pulse width modulating circuits 41, 42 give a controlled drivingduty ratio to the respective driving pulse circuits 12A to 12D of thegate driving circuit 120. The electric motor driving control means 40controls the driving duty ratio outputted from the pulse widthmodulating circuits 41, 42 on the basis of the driving electric currentarithmetic value Iest from the arithmetic means 60, and controls thedriving electric current value Imtr with respect to the electric motorMTR.

When the driving electric current target value Itag is given to theelectric motor driving control means 40, the electric motor drivingcontrol means 40 basically controls the operations of the pulse widthmodulating circuits 41, 42 and controls the driving electric currentImtr of the electric motor MTR by the gate driving circuit 120 such thatthe driving electric current value Imtr is equal to this drivingelectric current target value Itag. However, even when the drivingelectric current target value Itag is set to zero, the electric currentof a predetermined driving electric current offset value Ioff is flowedto the electric motor MTR. Accordingly, the driving electric currentvalue Imtr is corrected by the offset correction means 50.

A corrected driving electric current value Iamd given from the offsetcorrecting means 50 to the arithmetic means 60 is represented by thefollowing formula (1).Iamd=Imtr−Ioff  (1)

The arithmetic means 60 calculates the driving electric currentarithmetic value Iest by the following formula (2).Iest=Itag−Iamd=Itag−Imtr+Ioff  (2)

The offset correcting means 50 has two input sections 50 a, 50 b, oneinput-output section 50 c and one output section 50 d. The drivingelectric current detecting signal SImtr representing the drivingelectric current value Imtr from the electric motor electric currentdetecting circuit 130 is converted into a digital signal by an A/Dconverter 51 and is inputted to the input section 50 a. An input means52 is connected to the input section 50 b. This input means 52 is aninput means called a serial communication interface (SCI), and thedriving electric current offset value Ioff of high accuracy from theelectric motor driving electric current measuring circuit MCM isinputted in a digital format to this input means 52 through acommunication means 53. A nonvolatile memory (EEPROM) 55 is connected tothe input-output section 50 c. The output section 50 d supplies acorrecting driving electric current signal SIamd representing thecorrected driving electric current value Iamd to the arithmetic means60.

The offset adjusting process of the driving electric current is executedin the manufacturing factory of the automobile or the automobile parts,or the repairing factory by using the electric motor driving electriccurrent measuring circuit MCM. In this offset adjusting process, thedriving electric current offset value Ioff is really measured with thecontroller CNT and the electric motor MTR combined with this controllerCNT as objects. This driving electric current offset value Ioff isadjusted such that the driving electric current target signal generatingmeans 30 of the controller CNT sets the driving electric current targetvalue Itag to zero. Then, the driving electric current value Imtr of thedriving electric current flowed to the electric motor MTR at this timeis really measured by the electric motor driving electric currentmeasuring circuit MCM. The electric motor driving electric currentmeasuring circuit MCM outputs the driving electric current measuringsignal SIPmtr of high accuracy, but the driving electric currentmeasuring signal SIPmtr provided by setting the driving electric currenttarget value Itag to zero becomes a driving electric current offsetsignal SIoff representing the driving electric current offset valueIoff.

This driving electric current offset signal SIoff from the electricmotor driving electric current measuring circuit MCM is supplied to theinput means 52 through the communication means 53, and is stored andheld in the nonvolatile memory 55 through the offset correcting means50. This driving electric current offset value Ioff is held in thenonvolatile memory 55 until the driving electric current offset valueIoff is readjusted thereafter.

The ROM 70 of the microcomputer 20 includes a program for fetching thedriving electric current offset signal SIoff from the input means 52 tothe offset correcting means 50, and a program for storing and holdingthe fetched driving electric current offset value Ioff in thenonvolatile memory 55. The fetching operation of the driving electriccurrent offset signal SIoff to the offset correcting means 50, and thestoring and holding operations of the offset value Ioff to thenonvolatile memory 55 are executed by using these programs of the ROM70.

After the offset adjusting process is terminated in the manufacturingfactory of the automobile or the automobile parts, or the repairingfactory, the offset correcting means 50 of the controller CNT mounted tothe automobile calculates the corrected driving electric current valueIamd on the basis of the formula (1) in an operating state of theautomobile. In this case, the driving electric current value Imtr isfetched from the driving electric current detecting signal SImtr fromthe driving electric current detecting circuit 130 assembled into thecontroller CNT. In this operating state of the automobile, thearithmetic means 60 calculates the driving electric current arithmeticvalue Iest by the formula (2), and the driving electric current valueImtr of the electric motor MTR is controlled on the basis of thisdriving electric current arithmetic value Iest.

FIG. 2 shows a flow chart of the adjusting process of the drivingelectric current offset in the embodiment 1. This flow chart of FIG. 2includes ten steps from step S1 to step S10. As mentioned above, theadjusting process of this offset is executed in the manufacturingfactory of the automobile or the automobile parts, or the repairingfactory. The controller CNT is separated from the steering torque sensor31, the network 33 within the automobile, and the direct current powersource BAT, and is connected to a direct current power source within afactory similar to the direct current power source BAT.

First, in the step S1, instructions of the offset adjustment are givenfrom the communication means 53 to the controller CNT by using aninstruction signal INS. These offset adjusting instructions are fetchedto the microcomputer 20 through the input means 52 and the offsetcorrecting means 50. The microcomputer 20 stops control based oninformation from the steering torque sensor 31 and the network 33 withinthe automobile. In the next step S2, the driving electric current targetsignal generating means 30 generates a driving target signal SItag withthe driving electric current target value Itag as zero.

In the next step S3, the electric motor driving electric currentmeasuring circuit MCM measures the driving electric current of theelectric motor MTR corresponding to the driving electric current targetvalue Itag=0, and generates an offset signal SIoff (digital)representing the driving electric current offset value Ioff of theelectric motor MTR. In a step S4, this offset signal SIoff is inputtedfrom the communication means 53 to the offset correcting means 50through the input means 52.

In the next step S5, the offset correcting means 50 stores the drivingelectric current offset value Ioff to the nonvolatile memory 55 on thebasis of the fetched offset signal SIoff. In a step S6, the offsetcorrecting means 50 calculates and outputs a corrected driving electriccurrent value Iamd by using a detecting signal SImtr from the electricmotor electric current detecting circuit 130 and the driving electriccurrent offset value Ioff stored and held in the nonvolatile memory 55.At this time, since the driving electric current target value Itag=0 isset, an arithmetic value Iest=Iamd=Imtr−Ioff is outputted from thearithmetic means 60.

In the next step S7, the electric motor driving control means 40controls the operation of the electric motor MTR through the pulse widthmodulating circuits 41, 42, the gate driving circuit 120 and the switchcircuit 110 on the basis of the arithmetic value Iest from thearithmetic means 60. In a step S8, the driving electric current valueImtr of the electric motor MTR is again measured by using the electricmotor driving electric current measuring circuit MCM.

In the next step S9, it is judged whether the driving electric currentvalue Imtr of the electric motor measured in the step S8 lies within apredetermined tolerance or not. If this judging result is “yes”, theinstructions of termination of the offset adjustment are given by aninstruction signal INS from the communication means 53 in a step S10,and the offset adjusting process is terminated. In contrast to this,when the judging result of the step S9 is “no”, it is returned to thestep S4, and the adjustment of the driving electric current offset isagain made. At the readjusting time, a driving electric current offsetsignal SIoff (n) based on the measuring result in the step S8 is sentout in the step S4. In the step S5, a new driving electric currentoffset value Ioff is stored to the nonvolatile memory 55 on the basis ofthe driving electric current offset signal SIoff (n−1) sent out in theprevious step S4 and the above driving electric current offset signalSIoff (n).

As mentioned above, in the electrically operated power steeringcontroller in the embodiment 1, the offset correcting means 50 has thefirst input section 50 a and the second input section 50 b. The drivingelectric current detecting signal SImtr from the driving electriccurrent detecting circuit 130 is inputted to the first input section 50a. The input means 52 for inputting the driving electric current offsetsignal SIoff representing the driving electric current offset value Ioffis connected to the second input section 50 b. Accordingly, the drivingelectric current offset signal SIoff repsenting the driving electriccurrent offset value Ioff of high accuracy can be introduced from thisinput means 52 irrespective of the driving electric current detectingcircuit 130. Thus, the operation of the electric motor MTR can becontrolled with higher accuracy by using this driving electric currentoffset value of high accuracy.

Further, in the embodiment 1, the driving electric current offset signalSIoff is fetched to the offset correcting means 50 by the program storedto the ROM 70 of the microcomputer 20, and is stored and held in thenonvolatile memory 55. Accordingly, the fetching operation of thedriving electric current offset value Ioff and the storing and holdingoperations can be simply performed. In addition, the memory 55 is anonvolatile memory and can reliably hold the driving electric currentoffset value Ioff until the driving electric current offset value Ioffis next rewritten.

Further, in the adjusting method of the driving electric current offsetin the electrically operated power steering controller in the embodiment1, the driving electric current measuring means 300 different from thedriving electric current detecting means 13 is used and the offsetelectric current signal SIoff representing the driving electric currentoffset value Ioff is inputted to the offset correcting means 50 throughthe input means 52 by this driving electric current measuring means 300.Accordingly, the driving electric current offset signal SIoffrepresenting the driving electric current offset value Ioff of highaccuracy can be introduced into the electrically operated power steeringcontroller by setting the measuring accuracy of the driving electriccurrent measuring means 300 to be higher than the detecting accuracyusing the driving electric current detecting means 13 and the A/Dconverter 51. Thus, the electrically operated power steering controllercan control the operation of the electric motor with higher accuracy byusing this driving electric current offset value of higher accuracy.

Further, in the adjusting method of the driving electric current offsetof the electrically operated power steering controller in the embodiment1, since the driving electric current offset signal SIoff is fetched tothe offset correcting means 50 through the input means 52 as a digitalsignal, noise resisting characteristics of the driving electric currentoffset signal SIoff can be also improved.

Embodiment 2

This embodiment 2 is an embodiment corresponding to a second aspect ofthis invention, and includes an electrically operated power steeringcontroller in this invention, and an adjusting method of the drivingelectric current offset in the electrically operated power steeringcontroller in this invention.

FIG. 3 is a block diagram showing the electrically operated powersteering controller in this embodiment 2. In the electrically operatedpower steering controller in this embodiment 2, an offset signalgenerating means 50A is substituted for the offset correcting means 50in the embodiment 1, and the driving electric current detecting signalSImtr reprenting the driving electric current value Imtr of the electricmotor MTR from the electric motor driving electric current detectingmeans 13 is directly inputted to the arithmetic means 60. The otherconstructions are the same as the embodiment 1.

In the offset signal generating means 50A of FIG. 3, the input section50 a is omitted. This offset signal generating means 50A of FIG. 3 hasan input section 50 b connected to the input means 52, an input-outputsection 50 c connected to the nonvolatile memory 55, and an outputsection 50 d connected to the arithmetic means 60.

In the adjusting process of the driving electric current offset similarto that in the embodiment 1, a driving electric current offset signalSIoff representing a driving electric current offset value Ioff measuredwith high accuracy by the electric motor driving electric currentmeasuring means 300 is fetched from the input means 52 to the offsetsignal generating means 50A in the input section 50 b of the offsetsignal generating means 50A, and is stored and held in the nonvolatilememory 55. The offset signal generating means 50A generates the drivingelectric current offset signal SIoff representing the driving electriccurrent offset value Ioff of high accuracy in the output section 50 d ofthis offset signal generating means 50A, and supplies this drivingelectric current offset signal SIoff to the arithmetic means 60.

In the embodiment 2, the arithmetic means 60 calculates a drivingelectric current arithmetic value Iest on the basis of the followingformula (3) by using a driving electric current target signal SItagrepresenting a driving electric current target value Itag from thedriving electric current target signal generating means 30, a drivingelectric current detecting signal SImtr representing a driving electriccurrent value Imtr from the driving electric current detecting means 13,and the driving electric current offset signal SIoff representing thedriving electric current offset value Ioff from the offset signalgenerating means 50A.Iest=Itag−Imtr+Ioff  (3)

In the adjusting process of the driving electric current offset, drivingelectric current target value Itag=0 is set. Accordingly, the arithmeticvalue Iest using the following formula (4) is calculated.Iest=−Imtr+Ioff  (4)

The adjusting process of the driving electric current offset of theelectrically operated power steering controller of this embodiment 2 isexecuted by the flow chart of FIG. 4. Similar to the embodiment 1, thisadjusting process of the driving electric current offset is executed inthe manufacturing factory of the automobile or the automobile parts, orthe repairing factory.

Steps S1 to S4 of FIG. 4 are the same as steps S1 to S4 of FIG. 2, andsteps S8 to S10 of FIG. 4 are also the same as steps S8 to S10 of FIG.2.

In a step S51 of FIG. 4, the offset signal generating means 50A storesthe driving electric current offset value Ioff of high accuracy from thedriving electric current measuring means 300 to the nonvolatile memory55. In a step S61, the offset signal generating means 50A generates thedriving electric current offset signal SIoff representing the drivingelectric current offset value Ioff of high accuracy in the outputsection 50 d. In a step S71, the electric motor driving control means 40drives the electric motor MTR by the difference between the arithmeticvalue Iest based on the formula (4), i.e., the driving electric currentvalue Imtr and the driving electric current offset value Ioff of highaccuracy.

As mentioned above, in the embodiment 2 of the electrically operatedpower steering controller in this invention, it is constructed such thatthe driving electric current detecting signal SImtr from the electricmotor driving electric current detecting means 13 and the drivingelectric current offset signal SIoff from the offset signal generatingmeans 50A are supplied to the arithmetic means 60 from routes differentfrom each other. Further, the input means 52 for inputting the drivingelectric current offset signal SIoff representing the driving electriccurrent offset value Ioff is connected to the offset signal generatingmeans 50A. Accordingly, the driving electric current offset signal SIoffrepresenting the driving electric current offset value Ioff of highaccuracy can be introduced from this input means 52 irrespective of thedriving electric current detecting means 13. Thus, the operation of theelectric motor can be controlled with higher accuracy by using thisdriving electric current offset value of high accuracy.

Further, similar to the embodiment 1, the driving electric currentoffset signal SIoff is fetched to the offset signal generating means 50Aby a program stored to the ROM 70 of the microcomputer 20 in theembodiment 2. Further, this driving electric current offset value Ioffis stored and held in the memory 55. Accordingly, the fetching, storingand holding operations of the driving electric current offset value Ioffcan be simply performed. In addition, the memory 55 is a nonvolatilememory and can reliably hold the driving electric current offset valueIoff until the driving electric current offset value Ioff is nextrewritten.

Further, in the adjusting method of the driving electric current offsetin the electrically operated power steering controller in the embodiment2, the driving electric current measuring means 300 different from thedriving electric current detecting means 13 is used, and the offsetelectric current signal SIoff representing the driving electric currentoffset value Ioff is inputted to the offset signal generating means 50Athrough the input means 52 by this driving electric current measuringmeans 300. Accordingly, the driving electric current offset signal SIoffrepresenting the driving electric current offset value Ioff of highaccuracy can be introduced into the electrically operated power steeringcontroller by setting the measuring accuracy of the driving electriccurrent measuring means 300 to be higher than the detecting accuracyusing the driving electric current detecting means 13 and the A/Dconverter 51. Thus, the electrically operated power steering controllercan control the operation of the electric motor with higher accuracy byusing this driving electric current offset value of higher accuracy.

Further, in the adjusting method of the driving electric current offsetof the electrically operated power steering controller in the embodiment2, since the driving electric current offset signal SIoff is fetched tothe offset correcting means 50 through the input means 52 as a digitalsignal, noise resisting characteristics of the driving electric currentoffset signal SIoff can be also improved.

Embodiment 3

In the embodiments 1 and 2, the direct current electric motor is used asthe electric motor MTR. However, in this embodiment 3, a three-phasebrushless alternating current electric motor is used, and an electricmotor driving electric current measuring circuit MCM is arranged in eachphase, and driving electric current offset values Ioff-a, Ioff-b, Ioff-cof the respective phases are stored and held in the nonvolatile memory55. Further, in accordance with this construction, the electric motordriving electric current detecting circuit 130 also detects drivingelectric current values Imtr-a, Imtr-b, Imtr-c of the respective phases.The other constructions are the same as the embodiment 1 or 2. Inaccordance with this embodiment 3, the driving electric current can becontrolled with high accuracy while the driving electric current offsetvalue of each phase of the three-phase alternating current electricmotor is independent in each phase and is corrected by the drivingelectric current offset values Ioff-a, Ioff-b, Ioff-c of high accuracyfrom the electric motor driving electric current measuring circuit MCM.

Embodiment 4

In the above embodiments 1 to 3, the driving electric current offsetsignal SIoff is supplied to the input means 52 through the communicationmeans 53. However, in the embodiment 4, a mode for supplying the drivingelectric current offset signal SIoff through a control network (CAN) 34is set. In this case, no input means 52 is required so that cost can bereduced.

The electrically operated power steering controller and the adjustingmethod of its driving electric current offset in this invention areutilized in a power steering device of the automobile.

1. An adjusting method of a driving electric current offset in an electrically operated power steering controller comprising: generating, by a driving electric current target signal generating means, a driving electric current target signal representing a driving electric current target value Itag for an electric motor for generating auxiliary steering torque; generating, by an electric current detecting means, a driving electric current detecting signal representing a driving electric current value Imtr of said electric motor; generating, by an offset correcting means, a corrected driving electric current signal representing a corrected driving electric current value Iamd provided by correcting the driving electric current value Imtr by using a driving electric current offset value Ioff of said electric motor when said driving electric current target value Itag is set to zero; and controlling, by an electric motor driving control means, the operation of said electric motor on the basis of the driving electric current target signal and the corrected driving electric current signal, wherein said offset correcting means generates the corrected driving electric current signal, and the offset correcting means has first and second input portions, and the driving electric current detecting signal is inputted to said first input portion, and input means for inputting a driving electric current offset signal representing the driving electric current offset value Ioff is connected to said second input portion, inputting the driving electric current offset signal representing the driving electric current offset value Ioff to said offset correcting means through said input means by a driving electric current measuring means, said driving electric current measuring means outputs an offset driving current signal representing the driving electric current offset value Ioff with accuracy higher than that of said driving electric current detecting means, and as a result, the corrected driving electric current signal is generated by using the driving electric current detecting signal detected by said electric current detecting means and the offset driving current signal with accuracy higher than that of said electric current detecting means outputted by said driving electric current measuring means.
 2. The adjusting method of the driving electric current offset in the electrically operated power steering controller according to claim 1, wherein said driving electric current measuring means has an electric current measuring device for measuring the driving electric current offset value Ioff with accuracy higher than that of said driving electric current detecting means, and an A/D converter for converting the driving electric current offset value Ioff into a digital signal as the offset driving current signal, and the offset driving current signal is inputted to said offset correcting means through said input means.
 3. An adjusting method of a driving electric current offset in an electrically operated power steering controller comprising: generating, by a driving electric current target signal generating means, a driving electric current target signal representing a driving electric current target value Itag for an electric motor for generating auxiliary steering torque; generating, by a driving electric current detecting means, a driving electric current detecting signal representing a driving electric current value Imtr of said electric motor; generating, by an offset signal generating means, a driving electric current offset signal representing a driving electric current offset value Ioff of said electric motor when said driving electric current target value Itag is set to zero; calculating, by an arithmetic means, an arithmetic value Iest=Itag−(Imtr−Ioff) on the basis of the driving electric current target signal, the driving electric current detecting signal and the driving electric current offset signal; and controlling, by an electric motor driving control means, the operation of said electric motor on the basis of the arithmetic value; wherein the electrically operated power steering controller is constructed such that the driving electric current detecting signal and the driving electric current offset signal are supplied to said arithmetic means from routes different from each other, and input means is connected to said offset signal generating means; the driving electric current offset signal representing the driving electric current offset value Ioff is inputted to said offset signal generating means through said input means by a driving electric current measuring means, said driving electric current measuring means measures the driving electric current offset value Ioff with accuracy higher than that of said driving electric current detecting means, and as a result, the arithmetic value Iest is calculated by using the driving electric current target signal, the driving electric current detecting signal detected by said driving electric current detecting means and the driving electric current offset signal with accuracy higher than that of the driving electric current detecting means outputted by said driving electric current measuring means.
 4. The adjusting method of the driving electric current offset in the electrically operated power steering controller according to claim 3, wherein said driving electric current measuring means has an electric current measuring device for measuring the driving electric current offset value Ioff with accuracy higher than that of said driving electric current detecting means, and an A/D converter for converting said driving electric current offset value Ioff into a digital signal, and the digital signal is inputted to said offset signal generating means through said input means.
 5. The adjusting method of the driving electric current offset in the electrically operated power steering controller according to claim 1, wherein the adjusting method executes a first step for generating the corrected driving electric current signal representing the value Iamd by using the driving electric current offset value Ioff outputted by said driving electric current measuring means when said driving electric current target value Itag is set to zero, and for driving the electric motor on the basis of the corrected driving electric current signal, and a second step for measuring the driving current value by using said driving electric current measuring means and for judging whether the driving current value measured in said first step lies within a predetermined tolerance or not, and if the driving current value does not lie within said predetermined tolerance, the adjusting method again executes said first step and said second step.
 6. The adjusting method of the driving electric current offset in the electrically operated power steering controller according to claim 3, wherein the adjusting method executes a first step for calculating the arithmetic value Iest by using the driving electric current target signal, the driving electric current detecting signal and the driving electric current offset signal when said driving electric current target value Itag is set to zero, and for driving the electric motor on the basis of the arithmetic value, and a second step for measuring the driving current value by using said driving electric current measuring means and for judging whether the driving current value measured in said first step lies within a predetermined tolerance or not, and if the driving current value does not lie within said predetermined tolerance, the adjusting method again executes said first step and said second step. 